As shown in FIG. 1, a stirling cycle machine having a conventional piston supporting structure is provided with a piston driving mechanism 2 for generating a driving force to reciprocate a piston 1, a case 4 having a cross head cylinder 3 in the upper part thereof for protecting the piston driving mechanism 2, the piston 1 having a piston seal 5 on the outer circumferential surface thereof and being reciprocated by the driving force generated by the piston driving mechanism 2, a cross head 6 for connecting the piston driving mechanism 2 to the piston 1 to transfer the driving force generated by the piston driving mechanism 2 to the piston 1, and a guiding cross head seal 7 installed on the outer circumferential surface of the cross head 6, for reciprocating in friction with the inner wall of the cross head cylinder 3 to prevent vibration of the piston 1 during the reciprocal movement of the piston 1. Reference numeral 8 denotes a displacer, reference numeral 9 denotes a radiator, reference numeral 10 denotes a regenerator, and reference numeral 11 denotes a heat absorbing portion.
In the stirling cycle machine provided with the conventional piston supporting structure, as shown in FIG. 1, the piston 1 having the piston seal 5 on the outer circumferential surface reciprocates while the cross head 6 for connecting the piston driving mechanism 2 to the piston 1 moves up and down in the cross head cylinder 3 formed in the upper part of the case 4, when a driving force is generated by the piston driving mechanism 2 in the case 4 to reciprocate the piston 1 in the stirling cycle machine.
The piston driving mechanism 2 includes a crank shaft 2a connected to a shaft of driving motor (not shown), a rotating plate 2b being coupled at the center portion thereof to the crank shaft 2a, a first shaft pin 2e mounted at a side portion of the rotating plate 2b, an arm 2c linked between the shaft pin 2e and a portion of the cross head 6 with a second shaft pin 2d linked thereto, an idle rotating plate 2f mounted at a side portion of the shaft pin 2e, and a driving shaft 2g for moving the displacer 8 vertically with a coupling 2i connected to the displacer rod 2h. The displacer rod 2h is arranged to pass through the hollow rod portion 1a of the piston 1.
Here, in some cases, the piston 1 vibrates by the driving force of the piston driving mechanism 2 in the driving direction while being reciprocated by the piston driving force of the piston driving mechanism 2. However, the guiding cross head seal 7, which is installed on the outer circumferential surface of the cross head 6 reciprocating in the cross head cylinder 3, is brought into frictional contact with the cross head cylinder 3 during the reciprocal movement of the cross head 3, thereby preventing the vibration of the piston 1.
The operation of the piston driving mechanism 2 will now be described. When the crank shaft 2a is driven by a motor, the rotating plate 2b rotates with the first shaft pin 2e displaced from the center of the rotating plate 2b. With the rotation of the shaft pin 2e, the arm 2c linked between the shaft pin 2e and a portion of the cross head 6 permits vertical movement of the piston 1 along with the cross head 6. At the same time, the idle rotating plate 2f is rotated eccentrically to rotate the displacer driving shaft 2g. The rotation of the displacer driving shaft 2g is translated to the linear movement of the displacer rod 2h by the coupling 2i. The displacer rod 2h penetrating the hollow rod portion la of the piston 1 allows the vertical movement of the displacer 8 along with the vertical movement of the piston 1. Thus, rotation of the crank shaft 2a enables the up and down movement of the cross head 6 and piston 1 by the rotating plate 2b, as well as linear movement of the displacer 8 by the rotation of the idle rotating plate 2f.
However, in the conventional piston supporting structure for a stirling cycle machine, the cross head seal 7 is installed on the outer circumferential surface of the cross head 6 to prevent the vibration of the piston 1 while the piston 1 is being reciprocated by the piston driving mechanism 2. However, though the vibration of the piston 1 is prevented by the cross head seal 7 in frictional contact with the inner wall of the cross head cylinder 3, the friction between the cross head seal 7 and the cross head cylinder 3 generates heat, thus requiring exploration of an additional method for radiating the heat. Another problem with the conventional piston supporting structure is difficulty in machining and dimension management of the cross head cylinder 3.